The human body functions through a number of interdependent physiological systems controlled through various mechanical, electrical, and chemical processes. The metabolic state of the body is constantly changing. For example, as exercise level increases, the body consumes more oxygen and gives off more carbon dioxide. The cardiac and pulmonary systems maintain appropriate blood gas levels by making adjustments that bring more oxygen into the system and dispel more carbon dioxide. The cardiovascular system transports blood gases to and from the body tissues. The respiration system, through the breathing mechanism, performs the function of exchanging these gases with the external environment. Together, the cardiac and respiration systems form a larger anatomical and functional unit denoted the cardiopulmonary system.
Various disorders may affect the cardiovascular, respiratory, and other physiological systems. Diseases and disorders of the cardiac and pulmonary systems, are among the leading causes of acute and chronic illness in the world. For example, heart failure (HF) is a clinical syndrome that impacts a number of physiological processes, including respiration. Heart failure is an abnormality of cardiac function that causes cardiac output to fall below a level adequate to meet the metabolic demand of peripheral tissues. Heart failure is usually referred to as congestive heart failure (CHF) due to the accompanying venous and pulmonary congestion. Congestive heart failure may have a variety of underlying causes, including ischemic heart disease (coronary artery disease), hypertension (high blood pressure), and diabetes, among others. Other cardiac disorders include cardiac rhythm disorders, such as bradycardia (a heart rhythm that is too slow) and tachyarrhythmia (a heart rhythm that is too fast).
Pulmonary diseases or disorders may be organized into various categories, including, for example, breathing rhythm disorders, obstructive diseases, restrictive diseases, infectious diseases, pulmonary vasculature disorders, pleural cavity disorders, and others. Symptoms of pulmonary dysfunction may include symptoms such as apnea, dyspnea, changes in blood or respiratory gases, symptomatic respiratory sounds, e.g., coughing, wheezing, and general degradation of pulmonary function, among other symptoms.
Breathing rhythm disorders involve patterns of interrupted and/or disrupted breathing. Sleep apnea syndrome (SAS) and Cheyne-Stokes respiration (CSR) are examples of breathing rhythm disorders. Breathing rhythm disorders may be caused by an obstructed airway or by derangement of the signals from the brain controlling respiration. Sleep disordered breathing is particularly prevalent and is associated with excessive daytime sleepiness, systemic hypertension, increased risk of stroke, angina, and myocardial infarction. Breathing rhythm disorders can be particularly serious for patients concurrently suffering from cardiovascular deficiencies.
Obstructive pulmonary diseases may be associated with a decrease in the total volume of exhaled air flow caused by a narrowing or blockage of the airways. Examples of obstructive pulmonary diseases include asthma, emphysema and bronchitis. Chronic obstructive pulmonary disease (COPD) refers to chronic lung diseases that result in blocked air flow in the lungs. Chronic obstructive pulmonary disease generally develops over many years, typically from exposure to cigarette smoke, pollution, or other irritants. Over time, the elasticity of the lung tissue is lost, the lung's air sacs may collapse, the lungs may become distended, partially clogged with mucus, and lose the ability to expand and contract normally. As the disease progresses, breathing becomes labored, and the patient grows progressively weaker. Many people with COPD concurrently have both emphysema and chronic bronchitis.
Restrictive pulmonary diseases involve a decrease in the total volume of air that the lungs are able to hold. Often the decrease in total lung volume is due to a decrease in the elasticity of the lungs themselves, or may be caused by a limitation in the expansion of the chest wall during inhalation. Restrictive pulmonary disease may be the result of scarring from pneumonia, tuberculosis, or sarcoidosis. A decrease in lung volume may be caused by various neurological and muscular diseases affecting the neural signals and/or muscular strength of the chest wall and lungs. Examples of neurological and/or muscular diseases that may affect lung volume include poliomyelitis and multiple sclerosis. Lung volume deficiencies may also be related to congenital or acquired deformities of the chest.
Pulmonary dysfunctions may also involve disorders of the pleural cavity and/or pulmonary vasculature. Pulmonary vasculature disorders may include pulmonary hypertension, pulmonary edema, and pulmonary embolism. Disorders of the pleural cavity include conditions such as pleural effusion, pneumothorax, and hemothorax, for example.
Pulmonary diseases may be caused by infectious agents such as viral and/or bacterial agents. Examples of infectious pulmonary diseases include pneumonia, tuberculosis, and bronchiectasis. Other non-infectious pulmonary diseases include lung cancer and adult respiratory distress syndrome (ARDS), for example.
Therapy may be more effectively delivered to a patient to alleviate the diseases and disorders discussed above if the patient's cardiopulmonary status is known. Methods and systems for controlling therapy based on cardiopulmonary status are desirable.